Means for desensitizing carbonless papers

ABSTRACT

The disclosed desensitizing agents, when combined with a suitable solvent, can be used to desensitize &#39;&#39;&#39;&#39;carbonless papers of the DTO/metal type wherein the DTO compound is encapsulated and is released for chemical interaction with a coreactant metal salt by rupture of the capsules. The preferred desensitizing agents are partial esters of ethylene diaminetetraacetic acid, which partial esters are soluble in suitable organic media and form stable, substantially colorless complexes with, for example, nickel salts. Various homologs and analogs of these partial ester derivatives are also operative in the invention, as are certain less preferred compounds, i.e., certain diamines, oximes, and vic.-dimercaptans. The preferred desensitizing agents are also useful for desensitizing &#39;&#39;&#39;&#39;carbonless&#39;&#39;&#39;&#39; papers of the leuco dye/acidic clay type.

United States Patent [191 Yarian Dec. 3, 1974 1 MEANS FOR DESENSITIZING CARBONLESS PAPERS [75] Inventor:

[73] Assignee: Minnesota Mining & Manufacturing Company, St. Paul, Minn.

[22] Filed: Nov. 23, 1973 [21] Appl. No.: 418,470

Related US. Application Data Dean R. Yarian, Afton, Minn.

[62] Division of Ser. No. 110,876, Jan. 29, 1971, Pat. No.

[52] US. Cl l17/36.8, 1l7/l.7, l l7/36.2, 260/334 UR [51] Int. Cl B4lm 5/00, C08g 51/26 [58] Field of Search l17/36.2, 36.8, 1.7;

31.8 R, 33.2 R, 30.6 R

[56] References Cited UNITED STATES PATENTS 3,262,386 7/1966 Gordon ll7/36.2 X

3,364,052 l/l968 Martino ll7/36.2 X

3,516,846 6/1970 Matson l17/36.8 3,784,394 l/l974 Bildusas et al. l17/l.7 3,809,668 5/1974 Yarian 260/334 UR OTHER PUBLICATIONS Martell et al., Chemistry of theMetal Chelate Compounds, Prentice-Hall, Inc., N.Y., 1952, pp. 510, 511, 537, 538,541 and 542.

Primary Examiner-Thomas J. Herbert, Jr. Attorney, Agent, or Firm-Alexander, Sell, Steldt & DeLaHunt 5 7 ABSTRACT The disclosed desensitizing agents, when combined with a suitable solvent, can be used to desensitize carbonless papers of the DTO/metal type wherein the DTO compound is encapsulated and is released for chemical interaction with a coreactant metal salt by rupture of the capsules. The preferred desensitizing agents are partial esters of ethylene diaminetetraacetic acid, which partial esters are soluble in suitable organic media and form stable, substantially colorless complexes with, for example, nickel salts. Various homologs and analogs of these partial'ester derivatives are also operative in the invention, as are certain less preferred compounds, i.e., certain diamines, oximes, and vic.-dimercaptans. The preferred desensitizing agents are also useful for desensitizing carbonless papers of the leuco dye/acidic clay type.

4 Claims, 2 Drawing Figures MEANS FOR DESENSITIZING CARBONLESS PAPERS This is a division of application Ser. No. 1 10,876 filed Jan. 29, 1971, now US. Pat. No. 3,809,668.

This invention relates to a means and method for desensitizing the pressure-activated interaction of imageforming reactants and coreactants and to paper sheets desensitized by this means. The invention is useful in the art of carbonless paper; that is, sheets of paper which form images corresponding to a pattern of pressure applied to their surfaces. See, for example, US. Pat. No. 2,548,366 (Green et al.), issued Apr., 1951. Typically, carbonless paper takes the form of a manifold copy sheet where individual sheets in the manifold are treated or coated, on at least one surface, with a material which reacts with a dye precursor or colorforming reactant. An aspect of this invention relates to a means and method for desensitizing or blocking out a portion of the color-reactive coating or treated area. A further aspect of this invention relates to a means and method for treating the entire surface of a selfcontained, self-imaging paper (see Example 18 of US. Pat. No. 3,516,846 [Matson] issued June, 1970) to preserve and render tamper-proof images already formed thereon, i.e., so that further pressure applied to the surface will not activate the image-forming reaction. The invention is particularlyuseful with carbonless systems in which the dye precursor is dithiooxamide (DTO) or DTO derivatives. Preferred embodiments of the invention are also useful in systems wherein the dye precursor is an electron donor material such as benzoyl leuco methylene blue, or similar leuco dyes or Michlers hydrol (see, for example, the Green et al. patent cited previously).

The carbonless paper described in the aforementioned Green et al. patent makes use of a color reaction wherein the leuco dye (electron dolor), which is encapsulated, is released upon rupture of the capsules to react with an acidic silicate or clay or the like (electron acceptor), which is coated on the copy sheet. According to US. Pat. No. 2,777,780 (Cormack et al.), issued Jan. 1957, portions of the electron acceptor coating can be desensitized with cationic quartemary ammonium salts, higher aliphatic or aryl amine acetates, high molecular weight primary amines and primary diamines such as dodecyl amine or'dodecyl diamine, or substituted oxazolines. All the specific chemical compounds taught by Cormack et al. to be desensitizers have limited utility. These compounds were chosen specifically to deactivate the clay (or other electron acceptor) in a leuco dye/clay reaction, and are inoperative or unsuitable for deactivating one or more of the reactants in a system using a DTO-type dye precursor and a salt of a metal such as nickel, copper, cobalt, or cadmium. Furthermore, several of the desensitizers disclosed by Cormack et al.. are ammonium salts and thus are too polar for use in typical printing ink compositions.

Thus, until this invention, a chemical means for desensitizing carbonless paper based on DTO/metalsalt chemistry was not available. Physical means, of course, have been developed for all carbonless paper systems, including the DTO/metal salt type. One physical system involves the masking of the image areas with a non-contrasting background such as dark blue, black, or purple. The colored image is simply indistinguishable from, or indiscemible because of, the background. An obvious disadvantage of this non-contrasting background method is that the background indiscriminately masks any intelligence entered in the background area, be it by pressure activation of the DTO/metal-salt reaction, or by pencil or pen. The industry much prefers a selective method which blocks out only the images obtained by the pressure-activated chemical interaction (i.e. capsule rupture) but not ordinary ink or pencil entries. Still another physical method is to provide a physical barrier between the dye precursor and the coreactant salts, e.g., with a varnish overcoat on top of the metal salt coating. Reliable quality control has proved to be extremely difficult to obtain with this method. Over a period of weeks or months, the DTO- type compound may penetrate through the varnish barrier to the metal salt beneath and form an image. Thus, the thickness of the varnish barrier is critical and involves careful adjustments of coating thickness that are inconvenient and impractical for commercial printing practice.

Many of the theoretically possible chemical means for desensitizing the DTO/metal-salt reaction have proved to be ineffective. For example, it should be theoretically possible to provide coatings containing metal salts (e.g., zinc salts) which would scavenge the DTO- type compound by forming colorless complexes. However, the reaction of, for example, nickel soaps with DTO or DBDTO, or N,N-bis(2-octanoyloxy ethyl) dithiooxamide (DOEDTO), or other commonly used DTO/metal-salt reactions, are so highly favored'that the zinc is an ineffective competitor and does not deactivate all the DTO, DBDTO, DOEDTO, etc. Similarly, poorly controlled results are obtained by overcoating the copy sheet with coatings of aluminum soaps, i.e., on top of the nickel-containing coreactive coating. Overcoating with various salts or soaps of chromium, cadmium, manganese, lead, iron, cobalt, tin, and copper also failed to achieve reliable and controllable desensitizing of the DTO/Ni reaction. In general, attempts to tie up DTO or its derivatives with a competing metal ion are no more effective and no more subject to quality control than the physical barrier method discussed previously. (DBDT is di-benzyl-DTO, i.e., N,N'- bis(benzyl )dithiooxamide.)

Theoretically, it should also be possible to provide a I means for deactivatingor tieing up the metal salt co reactant rather than the DTO-compound. However, several problems are inherent in this approach. First, the typical image reactions (e.g., DBDTO/nickel soap) are strongly favored. Even if the coreactant metal ions (e.g., Ni, Co, or Cu ions) were tied up in a fairly stable,

colorless or low-contrast colored chemical complex, it

is quite possible that the DTO-type compound could liberate the ions from the non-contrasting complex and form or re-form the highly colored DTO/metal-salt complex (DTO/Ni, DTO/Cu, DTO/Co, etc.) Second, a complexng agent for the coreactant metal ion would have tobe compatible with standard ink compositions used in letterpress, rubberplate, dry offset, and other printing methods using inks containing oily liquid carriers. Preferably, the complexing agent should also be soluble in the more highly volatile carriers used in flexographic inks. To restate this requirement, the complexing agent should be soluble in a variety of ink vehicles and/or plasticizers of varying viscosity and volatility used in the various printing processes. Third, the

action of the complexing agent should not be significantly interfered with by drying agents such as the cobalt salts used with standard drying oils. Fourth, the complexing agent should preferably be non-toxic and dermatologically inactive. Fifth, if the complexing agent is chemically modified to make it more compatible with oil, this chemical modification should be of a type which will not swell or deform rubber rollers in an inking train. Sixth, the complexing agent should react with the coreactant metal ion (e.g., Ni, Cu, Co, etc., ion) to form a stable, low-contrast complex, preferably a complex which is white, colorless, or very light in color, or a complex having a color which strongly contrasts with brown, black, purple, and other colors produced by DTO/metal-salt complexes. For example, if the complexing agent reacted with a nickel salt to produce a purple compound, the use of a complexing agent would not have significant advantages over the printed block-out system described previously. Seventh, the complexing agent should be suitable for use with the self-contained type of carbonless paper disclosed in Example 18 of the Matson patent, previously cited. That is, it should be possible to render this type of carbonless paper insensitive to pressure by applying the complexing agent or desensitizer after intelligence has been entered on the sheet. Eighth, and perhaps most important, coreactant metal salts (e.g., Ni soaps) will not readily react with a desensitizer except in the presence of a solvent (hereinafter referred to as a cosolvent") capable of dissolving both the desensitizing or complexing compound and the metal salt. Many conventional ink vehicles will not dissolve these metal salts.

The requirements relating to the different types of printing methods are very specific and can be conflicting. Thus, as pointed out previously, fiexographic printing normally involves an ink vehicle of high volatility, while letterpress and similar methods involve low volatility inks. However, in any of these printing methods, the ink must contain the aforementioned cosolvent and must also have good penetrating power, so as to penetrate the full depth of the nickel coating on the copy sheet, and preferably should be incapable of adversely affecting rubber rollers due to solvolytic or swelling action or other chemical or physical effects of this type.

The prior art relating generally to the complexing of nickel, copper, and cobalt ions, and other colorreactive heavy metal or transition metal ions, is not particularly helpful. An extremely wide variety of complexing compounds or ligands are known to be capable of tieing up ions of the transition metals, but many of these would be unsuitable for use in the present invention. One problem is that many of these ligands form relatively weak or unstable complexes with transition metal ions. The chemical literature does contain data relating to the stability of, inter alia, coordination compounds of metals and various ligands or chelating agents, but these data were generally derived from studies in aqueous media. Needless to say, the most widely used large-run printing systems do not employ water-based inks, but rather inks which employ organic vehicles of varying degrees of polarity, as well as volatility and viscosity. Some metal chelating agents such as ethylene-diamine tetracetic acid (EDTA) and derivatives thereof have been used as scavengers or stabilizers for various metal salts, and as plasticizers, in organic systems. Thus, amine salts of EDTA-type compounds have been used as stabilizers for the lead tetraethyl in leaded gasoline. See U.S. Pat. No. 2,901,335 (Fields et al.), issued Aug., 1959. EDTA has been reacted with a dialkanol amine and a fatty acid to provide an emulsifier useful in oily or oil-in-water rust proofing compositions. See U.S. Pat. No. 2,794,000 (Ruedrich), issued May 1957. Esters of EDTA have been suggested for use as plasticizers, e.g., in making tire stocks. See U.S. Pat. No. 2,428,353 (Bersworth), issued Oct., 1947. Amides of EDTA have been used to remove metal ion contaminants from monomers and polymers, the amide form being used to provide hydrocarbon solubility. See U.S. Pat. No. 3,234,173 (Mann et al.), issued Feb. 1966. None of these disclosures regarding the use of EDTA or its derivatives in organic systems is any clue whatever to whether the solubility requirements of various printing ink systems can be met and whether the chelating agents are as effective in organic media as they are in aqueous media. In fact, preliminary studies preparatory to this invention indicate that amides of EDTA and higher alkyl amines are almost insoluble in ester-type cosolvents (solvents for both the coreactant metal ion and the chelating agent), e.g., tributyl phosphate. Thus, the prior art relating to chelating agents generally has given no attention to, much less provided guidelines for, means for rendering typical chelating agents compatible with both ink vehicles and cosolvents for coreactant metal salts or soaps.

Accordingly, this invention contemplates, for desensitizing color-forming reactions, a desensitizing compound at least partially soluble in a cosolvent for coreactant metal salts (particularly soaps of nickel, cobalt, or copper) which forms a chemical complex which is more stable than the DTO/nickel (or DTO/Co or DTO/Cu) complex in organic media, which is compatible with various ink vehicles, and which forms a white, colorless, or other low-contrast material. This invention also contemplates the use, in printing carbonless paper, of various metal chelating agents which are compatible with cosolvents for the metal salts, wherein the cosolvents have widely varying volatility and polarity and viscosity characteristics, depending on the type of printing system to be used. This invention also contemplates carbonless paper desensitizers comprising chelating agents which are substantially non-toxic and do not cause contact dermatitis, and which are preferably non-hygroscopic. Among the printing methods contemplated for use with this invention are letterpress, rubberplate, dry offset, lithographic and flexographic. Among the ink vehicles contemplated for use with this invention are the usual oleaginous type and alcohols or the like of relatively high volatility. The use of ester-type plasticizers in inks of this invention is also contemplated, as will be explained subsequently.

Briefly, this invention involves the adaptation of a complexing or chelating agent for color-fonning metal salts such that the complexing agent is suitable for combination with a cosolvent for both the chelating agent and the color-forming metal salt and is preferably also suitable for combination with other ingredients commonly used in letterpress, dry offset, wet offset, rubber plate, and flexographic inks, or the like; whereby the complexing agent serves as a desensitizing agent for carbonless paper, action paper, carbonless manifold copy sheets, self-contained copy sheets, and

similar applications of dye precursor/coreactant chemistry. The desensitizing (complexing) agent should be capable of forming a chemical complex or chelate with a color-forming metal salt whereby the chelate or complex is (a) substantially colorless, white, or of a color which strongly contrasts with purple or'black, and is (b) more stable, in oleaginous or other organic media, than a DTO/metal salt complex. The preferred desensitizing agents of this invention also desensitize the electron acceptor which forms a color by interaction with a leuco dye or similar electron donor. The adaptation of the preferred desensitizing agents for use in this invention has also resulted in desensitizing compositions which satisfy the toxicity, solubility, dermatological activity, and color criteria described previously. Preferably, the desensitizing compositions are formulated so as to be non-hygroscopic. The preferred desensitizing agents suitable for use in the preferred desensitizing compositions are the partial esters of EDTA (ethylenediamine tetracetic acid) and various analogs and homologs thereof. These preferred agents are effective desensitizers for reactions between a DTO-type dye precursor (e.g., DTO, DBDTO, DOEDTO, etc.) and the conventionally used coreactant heavy metal salts, e.g., the soaps of nickel, copper, cobalt, or, less preferably, cadmium. These agents also desensitize the electron acceptors which produce a strong color upon interaction with leuco dyes or the like. Other organic polycarboxylic acid and/or polyalcohol derivatives, e.g., derivatives of citric or tartaric acid or the like, and nitriloacetic acid, have many of the desirable properties of the EDTA esters but are ordinarily too weak in their chelating effect to satisfy the criteria of this invention. This relatively low chelating or desensitizing effect also is apparent for lauric acid, oleic acid, cod liver oil, etc.

Three other classes of organic compounds have marginal utility in this invention, but are not preferred: (1) polyamines wherein at least one amino group is substituted on a carbon atom which is beta or gamma to a secondary or tertiary nitrogen, (2) compounds containing two adjacent carbonyls and/or oxime radicals, i.e., R- (CO)-(CO)R, R(CO)(C=NOH)-R, or R-(C=NOH)-(C=NOH)R (where R and R are organic radicals), and (3) vicinal dimercaptans. The compounds of classes (1) and (3) tend to be toxic or dermatologically active or hygroscopic. The compounds of class (2) are more suitable, but tend to produce yellowor pink-colored complexes, some of which do not provide the high contrast background of the substantially white or substantially colorless EDTA- ester/metal salt complexes. The preferred desensitizing agents of this invention are useful in a wide variety of printing inks and thus can provide production quantities of partially desensitized carbonless or action paper, carbonless manifold style business forms, or the like. These agents can also be dissolved in highly volatile cosolvents" (as described previously), thus forming a desensitizing composition useful for the selfcontained type of carbonless or action paper (see the aforementioned Matson patent).

The invention and its application to manifold-style business forms and self-contained carbonless or action paper (i.e., the self-marking paper of Example 18 FIG. 1 is a perspective view of a manifold-style business form printed and used according to the present invention, and

FIG. 2 is a side elevational view illustrating a means and method for desensitizing self-marking paper, the self-marking paper being shown in cross-section and greatly enlarged in thickness.

Referring to the drawings, FIG. 1 shows a manifoldstyle business form 11 containing an original or top sheet and two copy sheets. As is conventional in the art,

the top sheet is coated, on its reverse surface only, with a layer 13 of encapsulated dye precursor, in this case a microencapsulated DTO-type compound, specifically N,N-bis(dibenzyl) dithiooxamide. As is conventional in carbonless paper utilizing DTO-type dye precursors, a cosolvent capable of dissolving both the DTO derivative and a coreactant metal salt is also encapsulated and included within layer 13. The first copy sheet has a similar coating 23 on its reverse surface. The obverse surfaces 25 and 27 of the second and third copy sheets, respectively, are coated with nickel rosinate, which, upon rupture of microcapsules in the coating 13 or 23 reacts with the DTO derivative and cosolvent physically liberated thereby and forms purple or blueblack images. The microcapsules in layer 13 or 23 are ruptured by the pressure of the ballpoint pen or pencil used to enter the data in the various columns of the original or top sheet of manifold form 11. A significant feature of manifold form 1 l is that it contains provision for two columns of numerical data, these columns being designated on the top sheet of the form 11 by reference numerals 15 and 19, and of these, the information in column 19 is intended to be confidential. Accordingly, the first copy sheet contains a desensitizing layer 17 which prevents images (corresponding'to the numerical data in column 19) from being formed only in the area corresponding to column 19 of the top sheet; hence, the data of column 15 do appear on this first copy sheet. 'The second copy sheet, which is intended to be an exact duplicate of the original or top sheet, is not provided with the desensitizing layer; therefore, all the data entered on the original in ball point pen or pencil do appear, including the data of column 19. In manifold form 11, layer 17 has been provided by running the first copy sheet through a letterpress inked with the trimethylester of ethylenediamine tetracetic acid (EDTA), the EDTA ester being dissolved in dibutylphthalate (DBP) and mixed with a suitable ink base. The blocked out area covered by layer' 17 is printed in proper register with the area corresponding to column 19 by conventional multi-station printing techniques. (These techniques ensure that layer 17 will not overlap column 15 of the first copy sheet.)

In an alternative embodiment of FIG. 1, coatings 13 and 23 comprise a microencapsulated electrondonating dye precursor such as a leuco dye, and the coatings on obverse surfaces 25 and 27 comprise an electron-acceptor, such as attapulgite clay; see U.S. Pat. No. 2,777,780, cited previously. in this leuco dye embodiment, layer 17 is, nevertheless, comprised of the same EDTA tri-ester and is provided in the same manner.

In FIG. 2, a self-marking paper sheet-31 made according to Example l8 of U.S. Pat. No. 3,516,846, containing the encapsulated DTO derivative and encapsulated cosolvents 35, and further containing nickel rosinate distributed throughout the thickness of the sheet, is shown being desensitized with a brush applicator 39 containing, in reservoir 41 (shown in phantom), the trimethylester of EDTA dissolved in ethyl alcohol, i.e., the desensitizing composition 43. The desensitizing composition 43 flows onto the surface of paper 31 through the brush 33 and penetrates deeply into and through paper 31. As a result of this penetration, the nickel rosinate is rendered inactive or desensitized. However, the ethyl alcohol in the desensitizing composition 43 evaporates rapidly, and the already-recorded information, represented by image 37, is not substantially affected by the desensitizing treatment. In one form of the embodiment shown in FIG. 2, the applicator 39 is set up as an after-treatment station for the print-out from a computer, thereby rendering tamperproof the print-out information 37 on the self-marking paper 31. As is readily apparent to those skilled in the art, the desensitizing method of FIG. 2 can also be applied to the copy sheets in manifold form 11 of FIG. 1.

The preferred practice of this invention involves the use in printing inks or the like, of desensitizing agents capable of chelating metals in metal salts such as M,, Z,,,, where M is nickel, cobalt, copper or the like, Z is a suitable organic or inorganic (e.g., Cl, Br, N 80,, etc.) anion, z is the valence of Z and m is the valence of M. Examples of suitable organic anions are the anions of C C aliphatic and cycloaliphatic carboxylic acids, including the rosin acids (e.g., abietic acid) and saturated and unsaturated fatty acids. The preferred desensitizing agents are compounds of the formula:

wherein X is a divalent aliphatic or cycloaliphatic radior a cyclic radical, such as cyclopentane, cyclohexane, etc., wherein the nitrogens are substituted 1,2- or 1,3-; A, B, C, and D are selected from the following group of substituents:

hydrogen, an aliphatic or cycloaliphatic group,

CH, COOH, each of these groups must be present as at least one, but not all, of A, B, C, and D CH, COOR (where R is aliphatic, preferably a lower alkyl group such as methyl, ethyl, propyl, isopropyl, or butyl, optimum results being obtained with methyl), and

where X is similar to X, E and F are similar to A, B, C, and D; E or F can therefore be another -X-N- (E)(F) unit, such that structures of the following type are formed:

where a is 0, l, 2, 3, 4, or other small integer.

For convenience, the compound ferred to as ethylenediaminetetraacetic acid (EDTA), its common name. It is to be understood that this is the same compound indexed by Chemical Abstracts under the name (ethylenedinitrilo)tetraacetic acid. Throughout this specificaion, the common nomenclature is used, both the EDTA and its homologs and analogs.

As pointed out previously, other COOH, COOR. and/or OH containing compounds are marginally operative, but not preferred for use in this invention, examples being derivatives of tartaric acid, citric acid, nitrilotriacetic acid, and the like, which are soluble in non-aqueous media. It is an essential feature of this invention that the desensitizing agent be capable of forming a chemical complex (i.e., coordination compound with chelate-like stability) with coreactant metal salts such that this complex has at least as much stability as complexes of DTO or derivatives thereof with these same coreactant metal salts. The metal salts which are suitable for practical commerical use, e.g., cobalt, nickel, and copper, form very stable colored complexes with DTO or its derivatives in the following order of stability (least to greatest): DTO/Co, DTO/Ni, DTO/Cu. Since nickel is so typical in its behavior, the magnitude of the stability of the DTO/Ni complex can serve as a reference point for the essential requirements of this invention. (The color-reactive DTO derivatives with dye precursor utility, e.g., the N,N-diorgano-substituted DTO derivatives, behave in a manner which is chemically analogous to DTO itself; these derivatives vary primarily as to their solubility characteristics, their vapor pressure, and the color of the complexes they form with a given metal.) Throughout this specification, the term DTO, DTO-type compound, or DTO derivative is used to describe dithiooxamide itself and its color-reactive derivatives with dye precursor utility, particularly the N,N-di-organo- DTO derivatives.

To provide an approximate indicator for the degree of metal chelate stability required for organic media, reference is made to a body of chemical literature consisting of studies in aqueous media, which have developed the basic mathematics used in measuring stability constants for coordination compounds, chelates, and similar chemical complexes and compounds containing metals.

The stability constants for the step-wise additions of ligands (K K etc.), e.g., protonated ligands, and the cumulative or gross addition of ligands (B) are defined in a publication of the Chemical Society (London) entitled Stability Constants, published in 6. See particularly pages xii xix of this publication. A further discussion of these stability constants, including tabulated log K or log K, log etc. values and log B values, can be found in an Introduction to Coordination Chemistry, Second Ed., by D. P. Graddon, Pergamon Press, 1968. Although these stability constant values are for aqueous media, it has been found that if, for a particular chelate, the log K (log K,, log K etc.) values are in excess of about 9 (preferably at least ll), there is some assurance that the nickel (or copper or cobalt) chelate will be stable in oleaginous or other organic media, even in the presence of a DTO-type compound. Stated another way, it has been found that citric and tartaric acids, known chelating agents for nickel, suitably moditied for solubility in organic media, are marginally operative in this invention. Therefore, a suitable desensiflexographic use (e.g., containing volatile vehicles boiling at less than 125 C., examples of such vehicles are ethanol and mixtures of ethanol and water.) Ethanol can also serve as the cosolvent, as can methanol,

tizing ink for commercial practice should contain a complexing or a chelating agents (i.e., desensitizing agent) which forms a complex with nickel ions that is more stable than those formed by citric or tartaric acids in such organic media.

Three classes of compounds, in addition to the J. L L J.

where:

R, R, R", and R' are hydrogen or a suitable aliphatic or cycloaliphatic group;

O is a suitable organic radical,

a and c are 2 or 3, and

bis 0, l, 2, 3 10, provided, that ifb=0, a+cis 2. compounds containing two adjacent carbonyls and/or oxime radicals, i.e., R-(CO)(CO)R, R(CO)-(C=NOH)R, or R(C=NOH)(C- =NO I-I)R where R and R are suitable organic radicals such as aliphatic, cycloaliphatic, or aromatic groups, and

3. vicinal dimercaptans, i.e., HS-RSH, where R is a l,2-disubstituted aliphatic, cycloaliphatic, or aromatic group.

Of these three classes, class (2) has the least disadvantages.

Broadly speaking, this invention has these aspects:

First, a desensitizing. composition for carbonless" paper (which could be in the form of a latterpress, rubber plate, dry offset, lithographic, or flexographic inklike material or other ink material suitable for large and small printing runs); second, printed carbonless paper forms (such as form 11 of FIG. -I) which have been at least partially desensitized during the printing run; and, third, a method of desensitizing selfcontained, self-marking carbonless paper, as shown in FIG. 2.

The desensitizing composition, to be pracitical,

should contain a cosolvent," i.e., an organic liquid capable of serving as a solvent and reaction medium for the desensitizing agent and the coreactant metal salt, e.g., the nickel, copper, or cobalt soap. These desensitizing compositions are of three basic types: (a) ink-like materials suitable for letterpress, rubber plate, and dry" offset printing, (b) materials similar to (a) but suitably modified for lithographic or wet offset, (c) materials similar to (a) or (b), but suitably modified for propanol, and other alcohols, cyclohexane, acetone, acetonitrile, nitromethane, and the like. The type (c) compositions can be modified for use in the aforementioned method which is described in FIG. 2.

In compositions of types (a) and (b), the cosolvent is preferably an ester-type plasticizer, e.g., the dialkyl esters of phthalic acid (such as dibutyl phthalate); organic esters of phosphoric acid, e.g., trialkyl phosphates (such as tributyl phosphate or trioctylphosphate) and tributoxyethylphosphate; ester and/or ether derivatives of diethylene glycol (e.g., Carbitol acetate, Methyl Cellosolve, etc. and compounds of the formula RCOOR', where R and R are aliphatic or cycloaliphatic, e.g., butyl acetate, rosin acid esters, propyl propionate, etc. Furthermore, in these compositions, an ink binder or viscosity modifying agent is normally used. Common examples are the drying oils (tung 'oil, etc.). Particulate synthetic resins (e. g., the polyure thanes commonly used in the art), and resin acid esters can also serve this function; all of these tend to set to an insoluble substance upon drying or curing of the ink. It is common practice to include accelerators, e.g., driers, to facilitate curing of the drying oils. Metal salt driers are pemissible, but less preferred in this invention. Silicones, mineral oil, and the like are also used to modify viscosity, but do not set in this manner. When an ink vehicle is included in addition to the previously described components, the vehicle should be of low volatility in compositions of type (a) and (b) and of high volatility in type (c). In types (a) and (b), the usual oleaginous vehicles can be used, e. g., high boiling hydrocarbon oils.

As is conventional in the art, suitable pigments and fillers can be added to the desensitizing ink compositions, e.g., carbon black, titanium dioxide, and other commonly used pigments and fillers.

In compositions of type (c), synthetic resin binders are preferred and suitable types of viscosity modifiers can also be added, as can the aforementioned pigments and fillers. It is to be noted that, although the vehicle and cosolvent in the type (c) compositions could be the same organic liquid, it is also permissible to add ester-type plasticizers to flexographic ink compositions.

Typical examples of desensitizing compounds of the polyamine, di-carbonyl or -oxime, and dimercaptan types described previously are commercially available, e.g., triethylenetetraamine, tetramethylethylenediamine, dimethylglyoxime, and l,2-dimercaptoethane.

The compound EDTA is also readily available, and itsnumber of carboxyl radicals in the polycarboxylic acid precursor. The preferred esterifying agents are alkanols, e.g., lower alkanols, such as methanol, ethanol, propanol, butanol, etc. Mixed esters (e.g., methylethyl, ethyl-butyl, etc.) can be provided by conventional ester interchange reactions.

Desensitizing compositions can be made up for use in this invention by combining 399 percent by weight of desensitizing agent with 199 percent by weight of cosolvent and -96 percent by weight of one or more ingredients from a suitable conventional ink base (e.g., tung oil, accelerators, silicone oils, liquid hydrocarbon vehicles, and rosin esters). More specifically, desensitizing ink compositions can be made by combining 360 percent by weight of desensitizing agent with 1-40 percent by weight of cosolvent and l5-90 percent by weight of one or more of the ingredients of the ink base.

The following non-limiting examples are illustrative of the invention. In these examples, all parts are by weight, unless otherwise indicated.

EXAMPLE A 4. A press-ready, air drying clear overprint varnish,

with drier. (Lawter ALVCO 2620W.)

5. A lithograhpic, air curing clear varnish with drier.

(Lawter l-lalex," a registered trademark.)

EXAMPLE B Desensitizing Ink Compositions for Letterpress For experimental letterpress printing runs, the following desensitizing compositions were used:

Parts by Weight ingredient Desensitizing Agent 5 20 Cosolvent 56 An lnk Base of Types l (5), supra The cosolvent was, except as otherwise indicated, tributylphosphate (TBP) or dibutylphthalate (DBP).

Control runs with a proof press (described subsequently) were made using this range of formulations, but omitting the desensitizing agents. These control runs failed to desensitize DTO/Ni-type Carbonless paper (3M Brand Carbonless Paper, Type 200).

EXAMPLES l V Experimental Printing Runs All experimental printing runs were made with a Vandercook Proof Press with light, medium and heavy pipette application of ink (lPI pipette). The Vandercook Proof Press is a scaled-down version of standard letterpress equipment. The sheets printed with the desensitizing ink were conventional nickel rosinatecoated receptor sheets (3M Brand Carbonless Paper, Type 200, CF [coated front] sheet). After the proof press run, a conventional donor sheet coated on its reverse surface with encapsulated DBDTO and solvent, i.e., a 3M Brand Carbonless Paper, Type 200 CB (coated back) sheet, was superimposed on the treated CF receptor sheet and typed on in the usual manner. The typing was done with CF sheets fresh from the proof press, as well as CF sheets which had been aged for at least a week. A sample printed CF sheet was considered effectively desensitized if an image failed to appear even a week or more after the typing or after accelerated aging tests involving brief exposures to C.

The results of the proof press trial runs for the desensitizing agents described previously in various ink compositions are summarized in the following Examples.

EXAMPLE I DlOXIME DESENSlTlZlNG AGENTS The following compositions:

% by Weight Component l0 Desensitizing agent (dioxime) 5 Tributylphosphate (TBP) 85 Ink Base: (l).( l

was tested with the rollowing results:

Desensitizing Agent Comments Effective, but turned CF sheet bright pink or reddish pink. The pink chelate and its ligand had a tendency to sublime Dimethylglyoxime Cyclohexanedione-dioximc Effective, but turned CF sheet a dark reddish pink The above composition was modified as follows:

This modified composition produced substantially the same results with the two di-oximes named previously.

EXAMPLE ll POLYAMINE DESENSITIZING AGENTS The following composition was used in this Example:

% by Weight Component The I'CSUIIS were 3.8 follows:

30 Desensitizing agent (Polyamine) 5 Cosolvent (TPB or DBP) Desensitizing Ink 65 Ink Base: (1), (2), (3), (4), or (5) Agent Compound Base Comments IV A (I)* Effective; CF sheet remained substantially colorless The results were as follows: IV A 2 do.

Desensitizing Agent Solvent Ink Base Result Comments Triethylenetetraamine TBP (1) Effective, but CF eventually turned yellow Triethylenetetraamine TBP (2) Effective, but CF turned brown Triethylenetetraamine TBP (3) Effective, but CF turned brown 5-ethyl-5(4-amino- 2-azabutyl-l,9- Effective; CF sheet diamin-3 ,7-diaza DBP (4) remained substantially nonane* colorless -ethyl-5(4-amino- 2-AZABUTYL)-l,9- Effective; CF sheet diamino-3 ,7-diaza- DBP (5) remained substantially nonane* colorless Tetramethylethylene- I e DBP (1) Effective; CF sheet dlamme remained substantially colorless *F. Lions et al, Inorg, Chem. 2 (3), p. 5 7 (1 EXAMPLE III IV A 3) do. IV -B (1) do. VIC. DIMERCA N DESENSITIZER IV C (l) Effective; CF sheet remained When 30. wt. percent of 2,3-dimercaptopropanol-l were combined with 65 wt. percent of ink base l (4),

or (5) and 5 wt.

percent DBP, the resulting compositions effectively desensitized the CF sheet, but turned its surface dark brown. The unpleasant odor and toxicity of the dimercaptan are further disadvantages.

EXAMPLE IV The following tested:

Compound No.

were the EDTA-type partial esters Name substantially colorless; Also effective with a standard clay-coated CF sheet and a leuco-dye CB sheet (NCR Carbonless Paper).

This composition was 24 wt. Compound lV-A, 20 wt. if DBP. and 56 wt. '1 ink base (I), instead of the 30/5/65 formulation used for the other runs.

Compound IVC (the EDTA trimethyl ester) was tested with a wide variety of cosolvents other than DBP, but'in the same 30/5/65 formulation described previously. All of the following cosolvents were found to be suitable:

Ethyleneglycolmonomethylether (Methyl Cello- Trimethyl ester, monoacid of trans-cyclohexane-l 2-diamine-N,N,N,N-tetraacetic acid Tetraethyl ester, monoacid of diethylenetriamine-N,N,N',N" -pentaacetic acid Trimethyl ester, monoacid of EDTA The composition used, unless otherwise indicated, 60

was as follows:

Wt. Component 30 Desensitizing Agent 5 Cosolvent (DBP) 65 Ink Base: (1), (2), or (3) EXAMPLE v MARGINALLY EFFECTIVE DESENSITIZING AGENTS Those liquids in the above list which boil at less than 125 C. can be used as vehicles as well as cosolvents, but higher boiling liquids preferably are present in minor amounts as cosolvents for the metal salt and Thirty percent by weight of the compounds to be 5 DTO mp un tested were combined with 5 wt. percent of cosolvent What S Claimed iSI and 65 wt. percent of the base ink. The results of the 1. A printed form comprising a paperlike sheet, trial runs were: a material present on at least part of a surface of said Compound Solvent Base lnk Effectiveness Citric acid Methyl Cellosolve (1) Fair (see Ex. lV) Citric acid do. (2) Poor Citric acid do. (3) Poor Tartaric acid do. 1) Fair Tartaric acid do. (2) Poor Tartaric acid do. (3) Poor Nitirilotriacetic Tributoxyethyl acid phosphate l Fair Nitrilotriacetic do. (2) Poor acid Nitrilotriacetic do. (3) Poor acid Although these marginally active materials were not paper-like sheet, said material being color-reactive particularly desirable for use in printing runs, they were with a dye precursor, and adequate, as solutions in ethanol, for desensitizing selfinteracted with at least a portion of said material, a contained, selfmarking paper in accordance with the complexing agent soluble in organic media and camethod illustrated in FIG. 2 of the Drawing. Apparpable of forming a coordination compound with a ently the mass action effect can be utilized in this salt or nickel, copper, cobalt, or cadmium, wherein method. Accordingly, desensitizing agents with a log K said complexing agent is capable of forming a comor log K of about 9-l2 are particularly suited to the plex in said organic media with coreactant salts method of FIG. 2. such that said complex is more stable than complexes of dithiooxamide or derivatives thereof with EXAMPLE W said metal salts. FLEXOGRAPHIC lNKS 2. A printed form according to claim 1 wherein said It was found that the desensitizing agents of the pret i l i a i k l i t coating, ceding Examples could be used in flexographic inks- 3. A printed form according to claim 1 wherein said Preferred flexographc inks comprised a water-ethanol material is an electron acceptor capable of forming a solvent medium serving as vehicle and cosolvent, a parcolor upon ti with a leuco dy ticulate synthetic resin binder, and the desensitizing 4. A method of desensitizing a self-marking, selfagents. Other suitable cosolvents which could be incontained carbonless paper containing an encapsulated cluded in the solvent medium were: dye precursor comprising dithiooxamide or a derivative dialkyl sulfones and dialkyl sulfoxides, e.g., dimethylthereof and a metal salt coreactive with said dye presulfoxide; aliphatic, cycloaliphatic, and aromatic cursor, said method comprising the step of applying to nitriles, e.g., acetonitrile, benzonitrile, etc.; a surface of said self-marking, self-contained carbonaliphatic nitro compounds, e.g., nitromethane; keless paper a composition comprising (1) a complexing tones of the formula CH COR, where R is an agent soluble in organic media and capable of forming aliphatic, cycloaliphatic, or aromatic group; ama complex in said organic media with said coreactant ides of the formula R CONR where R and R are metal salt such that said complex is more stable than hydrogen or an aliphatic group, e.g., dimethylformcomplexes of dithiooxamide or derivatives thereof with amide, dimethylacetamide, etc.; liquid alkanols; said metal salt, and (2) an organic liquid having a boiland phosphoric acid amides of the formula ing point less than 125 C. capable of dissolving said (R N) PO, where R is hydrogen or aliphatic. metal salt and said complexing agent.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 5 9" DATED December, 3, 1974 INVENTOR(SY) Dean R. Yarian It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 10, line 23, "resin" should be rosin In Column 13 line 22 (first column of the Table,

fourth entry), close the parenthesis after "2-azabutyl" so the line reads 2-azabutyl)-l,9- and line 56 (in the column headed "Name" second entry), before the N" insert another N' so that the line reads triamine-N,N,N' ,N' ,N" pentaacetic acid In Column 16 line 28 (Claim 1, line 8), after "salt" Signed and sealed this 3rd day of June 1975.

(SEAL) Attest:

v C. MARSHALL DANN RUTH C. MASON I Commissioner of Patents and Trademarks I Attesting Officer and before "nickel" change "or" to of 

1. A PRINTED FORM COMPRISING A PAPERLIKE SHEEET, A MATERIAL PRESENT ON AT LEAST PART OF A SURFACE OF SAID PAPERLIKE SHEET, SAID MATERIAL BEING COLOR-REACTIVE WITH A DYE PRECURSOR, AND INTERACTED WITH AT LEAST A PORTION OF SAID MATERIAL, A COMPLEXING AGENT SOLUBLE IN ORGANIC MEDIA AND CAPABLE OF FORMING A COORDINATION COMPOUND WITH A SALT OR NICKEL, COPPER, COBALT, OR CADMIUM, WHEREIN SAID COMPLEXING AGENT IS CAPABLE OF FORMING A COMPLEX IN SAID ORGANIC MEDIA WITH COREACTANNT SALTS SUCH THAT SAID COMPLEX IS MORE STABLE THAN COMPLEXES OF DITHIOOXAMIDE OR DERIVATIVES THEREOF WITH SAID METAL SALTS.
 2. A printed form according to claim 1 wherein said material is a nickel rosinate coating.
 3. A printed form according to claim 1 wherein said material is an electron acceptor capable of forming a color upon reacting with a leuco dye.
 4. A method of desensitizing a self-marking, self-contained carbonless paper containing an encapsulated dye precursor comprising dithiooxamide or a derivative thereof and a metal salt coreactive with said dye precursor, said method comprising the step of applying to a surface of said self-marking, self-contained carbonless paper a composition comprising (1) a complexing agent soluble in organic media and capable of forming a complex in said organic media with said coreactant metal salt such that said complex is more stable than complexes of dithiooxamide or derivatives thereof with said metal salt, and (2) an organic liquid having a boiling point less than 125* C. capable of dissolving said metal salt and said complexing agent. 